Process for preparing monomer complexes

ABSTRACT

Disclosed are processes for preparing monomer complexes that include contacting 2,3,5,6-tetraminopyridine free base in water with 2,5-dihydroxy terephthalic acid dipotassium salt to form an aqueous mixture, and adjusting the pH of the aqueous mixture to within the range of from about (3) to about (5) to precipitate the monomer complex. Processes of polymerizing the monomer complexes, polyareneazoles, filaments and yarns are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No.PCT/US2006/011262, filed Mar. 27, 2006, which claims the benefit of U.S.Provisional Application Nos. 60/665,776, filed Mar. 28, 2005, thedisclosure of which is incorporated herein by reference in it'sentirety.

FIELD OF THE INVENTION

The present invention generally relates to monomer complexes, rigid-rodpolymers and processes for the preparation of such polymers. Inparticular, the present invention relates to methods of preparingmonomer complexes that are used to make high viscosity rigid-rodpolymeric compositions that are suitable for spinning into filaments andyarns.

BACKGROUND OF THE INVENTION

Advances in polymer chemistry and technology over the last few decadeshave enabled the development of high-performance polymeric fibers. Forexample, liquid-crystalline polymer solutions of heterocyclic rigid-rodpolymers can be formed into high strength fibers by spinningliquid-crystalline solutions into wet fibers, removing solvent to drythe fibers, and heat treating the dried fibers. Examples ofhigh-performance polymeric fibers that include poly(p-phenylenebenzobisthiazole) (“PBZT”) and poly(p-phenylene-2,6-benzobisoxazole)(“PBO”).

Fiber strength is typically correlated to one or more polymerparameters, including composition, molecular weight, intermolecularinteractions, backbone, residual solvent or water, macromolecularorientation, and process history. For example, fiber strength typicallyincreases with polymer length (i.e., molecular weight), polymerorientation, and the presence of strong attractive intermolecularinteractions. As high molecular weight rigid-rod polymers are useful forforming polymer solutions (“dopes”) from which fibers can be spun,increasing molecular weight typically results in increased fiberstrength.

Molecular weights of rigid-rod polymers are typically monitored by, andcorrelated to, one or more dilute solution viscosity measurements.Accordingly, dilute solution measurements of the relative viscosity(“V_(rel)” or “η_(rel)” or “n_(rel)”) and inherent viscosity (“V_(inh)”or “η_(inh)” or “n_(inh)”) are typically used for monitoring polymermolecular weight. The relative and inherent viscosities of dilutepolymer solutions are related according to the expressionV _(inh)=ln(V _(rel))/C,where ln is the natural logarithm function and C is the concentration ofthe polymer solution. V_(rel) is a unitless ratio, thus V_(inh) isexpressed in units of inverse concentration, typically as deciliters pergram (“dl/g”).

Rigid-rod polymer fibers having strong hydrogen bonds between polymerchains, e.g., polypyridobisimidazoles, have been described in U.S. Pat.No. 5,674,969 to Sikkema et al. An example of a polypyridobisimidazoleincludespoly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole),which can be prepared by the condensation polymerization oftetraminopyridine and 2,5-dihydroxyterephthalic acid in polyphosphoricacid. Sikkema describes that in making one- or two-dimensional objects,such as fibers, films, tapes, and the like, it is desired thatpolypyridobisimidazoles have a high molecular weight corresponding to arelative viscosity (“V_(rel)” or “η_(rel)”) of at least about 3.5,preferably at least about 5, and more particularly equal to or higherthan about 10, when measured at a polymer concentration of 0.25 g/dl inmethane sulfonic acid at 25° C. Sikkema also discloses that very goodfiber spinning results are obtained withpoly[pyridobisimidazole-2,6-diyl(2,5-dihydroxy-p-phenylene)] havingrelative viscosities greater than about 12, and that relativeviscosities of over 50 (corresponding to inherent viscosities greaterthan about 15.6 dl/g) can be achieved. Accordingly, further technicaladvances are needed to provide even higher molecular weight rigid-rodpolymers, such as polypyridobisimidazoles, that are characterized asproviding polymer solutions having even greater viscosities.

As described further herein, the polypyridobisimidazole class ofrigid-rod polymers is a sub-genus of the polypyridazoles class ofrigid-rod polymers, which is a sub-genus of the polyareneazole class ofrigid-rod polymers. Accordingly, further technical advances are neededto provide even higher molecular weight polyareneazole rigid-rodpolymers.

SUMMARY OF THE INVENTION

The present invention provides processes for preparing a polyareneazolepolymer including contacting, in polyphosphoric acid, azole-formingmonomers and from about 0.05 to about 0.9 weight percent, based on thetotal weight of the azole-forming monomers, iron metal powder, andreacting the azole-forming monomers to form the polyareneazole polymer.

In other aspects, the present invention provides processes for preparinga polyareneazole polymer including contacting, in polyphosphoric acid,azole-forming monomers and from about 0.05 to about 0.9 weight percent,based on the total weight of the azole-forming monomers, metal powdercomprising vanadium metal, chromium metal, or any combination thereof,and reacting the azole-forming monomers to form the polyareneazolepolymer.

In certain aspects, the present invention also provides processes forpreparing a polyareneazole polymer, including contacting, inpolyphosphoric acid, an azole-forming monomer complex and tin metalpowder, the azole-forming monomer complex synthesized using a molarexcess of a first azole-forming monomer and a second azole-formingmonomer, the tin metal powder added in an amount of from about 0.05 toabout 0.9 weight percent, based on the total amount of azole-formingmonomer complex, and reacting the monomer complex to form thepolyareneazole polymer.

In other aspects, the present invention provides processes for makingmonomer complexes comprising 2,3,5,6-tetramino pyridine and2,5-dihydroxy terephthalic acid monomers, including the steps ofcontacting a 2,3,5,6-tetraminopyridine free base in water to a2,5-dihydroxy terephthalic acid dipotassium salt to form an aqueousmixture, and adjusting the pH of the aqueous mixture to within the rangeof from about 3 to about 5 to precipitate the monomer complex.

In certain aspects, the present invention provides processes for makingmonomer complexes composed of 2,3,5,6-tetramino pyridine and2,5-dihydroxy terephthalic acid monomers, including the steps ofcontacting a molar excess 2,3,5,6-tetraminopyridine free base in waterwith 2,5-dihydroxy terephthalic acid dipotassium salt to form an aqueousmixture, and adjusting the pH of the aqueous mixture to within the rangeof from about 3 to about 5 to precipitate the monomer complex.

In other aspects, the present invention provides for polyareneazolepolymers that are characterized as forming polymer solutions having aninherent viscosity of at least about 22 dl/g at 30° C. at a polymerconcentration of 0.05 g/dl in methane sulfonic acid.

In certain aspects, the present invention provides for filaments andmultifilament yarns prepared frompoly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole)polymers that are characterized as providing a polymer solution havingan inherent viscosity of at least about 22 dl/g at 30° C. at a polymerconcentration of 0.05 g/dl in methane sulfonic acid.

In other aspects, the present invention further provides processes forpreparing apoly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole)polymer, including the steps of contacting a molar excess of a2,3,5,6-tetramino pyridine free base in water to a 2,5-dihydroxyterephthalic acid salt to form an aqueous mixture, adjusting the pH ofthe aqueous mixture to within the range of from about 3 to about 5 toprecipitate a monomer complex composed of 2,3,5,6-tetramino pyridine and2,5-dihydroxy terephthalic acid monomers, contacting, in polyphosphoricacid, the monomer complex with metal powder, the metal powder added inan amount of from about 0.05 to about 0.9 weight percent, based on thetotal weight of the monomer complex, and polymerizing the monomercomplex in polyphosphoric acid to form the polymer solution.

In certain aspects, the present invention provides for preparing apoly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole)polymer, including the steps of contacting 2,3,5,6-tetramino pyridinefree base in water with 2,5-dihydroxy terephthalic acid dipotassium saltto form an aqueous mixture, adjusting the pH of the aqueous mixture towithin the range of from about 3 to about 5 to precipitate a monomercomplex composed of 2,3,5,6-tetramino pyridine and 2,5-dihydroxyterephthalic acid monomers, contacting, in polyphosphoric acid, themonomer complex with metal powder, the metal powder added in an amountof from about 0.05 to about 0.9 weight percent, based on the totalweight of the monomer complex, and polymerizing the monomer complex inpolyphosphoric acid to form the polymer solution.

Other aspects of the present invention will be apparent to those skilledin the art in view of the detailed description and drawings of theinvention as provided herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description, isfurther understood when read in conjunction with the appended drawings.For the purpose of illustrating the invention, there is shown in thedrawings exemplary embodiments of the invention; however, the inventionis not limited to the specific methods, compositions, and devicesdisclosed. In the drawings:

FIG. 1 is a schematic diagram of a polyareneazole fiber productionprocess.

FIG. 2 is a graphical representation of inherent viscosity versus tincontent of polyareneazole polymer solutions according to certainembodiments of the present invention that are listed in Table 4.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention may be understood more readily by reference to thefollowing detailed description taken in connection with the accompanyingfigures and examples, which form a part of this disclosure. It is to beunderstood that this invention is not limited to the specific devices,methods, conditions or parameters described and/or shown herein, andthat the terminology used herein is for the purpose of describingparticular embodiments by way of example only and is not intended to belimiting of the claimed invention. Also, as used in the specificationincluding the appended claims, the singular forms “a,” “an,” and “the”include the plural, and reference to a particular numerical valueincludes at least that particular value, unless the context clearlydictates otherwise. When a range of values is expressed, anotherembodiment includes from the one particular value and/or to the otherparticular value. Similarly, when values are expressed asapproximations, by use of the antecedent “about,” it will be understoodthat the particular value forms another embodiment. All ranges areinclusive and combinable. When any variable occurs more than one time inany constituent or in any formula, its definition in each occurrence isindependent of its definition at every other occurrence. Combinations ofsubstituents and/or variables are permissible only if such combinationsresult in stable compounds.

As employed above and throughout the disclosure, the following terms,unless otherwise indicated, shall be understood to have the followingmeanings.

Filaments of the present invention can be made from polyareneazolepolymer. As defined herein, “polyareneazole” refers to polymers havingeither:

one heteroaromatic ring fused with an adjacent aromatic group (Ar) ofrepeating unit structure (a):

with N being a nitrogen atom and Z being a sulfur, oxygen, or NR groupwith R being hydrogen or a substituted or unsubstituted alkyl or arylattached to N; ortwo hetero aromatic rings each fused to a common aromatic group (Ar¹) ofeither of the repeating unit structures (b1 or b2):

wherein N is a nitrogen atom and B is an oxygen, sulfur, or NR group,wherein R is hydrogen or a substituted or unsubstituted alkyl or arylattached to N. The number of repeating unit structures represented bystructures (a), (b1), and (b2) is not critical. Each polymer chaintypically has from about 10 to about 25,000 repeating units.Polyareneazole polymers include polybenzazole polymers and/orpolypyridazole polymers. In certain embodiments, the polybenzazolepolymers comprise polybenzimidazole or polybenzobisimidazole polymers.In certain other embodiments, the polypyridazole polymers comprisepolypyridobisimidazole or polypyridoimidazole polymers. In certainpreferred embodiments, the polymers are of a polybenzobisimidazole orpolypyridobisimidazole type.

In structure (b1) and (b2), Y is an aromatic, heteroaromatic, aliphaticgroup, or nil; preferably an aromatic group; more preferably asix-membered aromatic group of carbon atoms. Still more preferably, thesix-membered aromatic group of carbon atoms (Y) has para-orientedlinkages with two substituted hydroxyl groups; even more preferably2,5-dihydroxy-para-phenylene.

In structures (a), (b1), or (b2), Ar and Ar¹ each represent any aromaticor heteroaromatic group. The aromatic or heteroaromatic group can be afused or non-fused polycyclic system, but is preferably a singlesix-membered ring. More preferably, the Ar or Ar¹ group is preferablyheteroaromatic, wherein a nitrogen atom is substituted for one of thecarbon atoms of the ring system or Ar or Ar¹ may contain only carbonring atoms. Still more preferably, the Ar or Ar¹ group isheteroaromatic.

As herein defined, “polybenzazole” refers to polyareneazole polymerhaving repeating structure (a), (b1), or (b2) wherein the Ar or Ar¹group is a single six-membered aromatic ring of carbon atoms.Preferably, polybenzazoles include a class of rigid rod polybenzazoleshaving the structure (b1) or (b2); more preferably rigid rodpolybenzazoles having the structure (b1) or (b2) with a six-memberedcarbocyclic aromatic ring Ar¹. Such preferred polybenzazoles include,but are not limited to polybenzimidazoles (B═NR), polybenzthiazoles(B═S), polybenzoxazoles (B═O), and mixtures or copolymers thereof. Whenthe polybenzazole is a polybenzimidazole, preferably it ispoly(benzo[1,2-d:4,5-d′]bisimidazole-2,6-diyl-1,4-phenylene). When thepolybenzazole is a polybenzthiazole, preferably it ispoly(benzo[1,2-d:4,5-d′]bisthiazole-2,6-diyl-1,4-phenylene). When thepolybenzazole is a polybenzoxazole, preferably it ispoly(benzo[1,2-d:4,5-d′]bisoxazole-2,6-diyl-1,4-phenylene).

As herein defined, “polypyridazole” refers to polyareneazole polymerhaving repeating structure (a), (b1), or (b2) wherein the Ar or Ar¹group is a single six-membered aromatic ring of five carbon atoms andone nitrogen atom. Preferably, these polypyridazoles include a class ofrigid rod polypyridazoles having the structure (b1) or (b2), morepreferably rigid rod polypyridazoles having the structure (b1) or (b2)with a six-membered heterocyclic aromatic ring Ar¹. Such more preferredpolypyridazoles include, but are not limited to polypyridobisimidazole(B═NR), polypyridobisthiazole (B═S), polypyridobisoxazole (B═O), andmixtures or copolymers thereof. Yet more preferred, the polypyridazoleis a polypyridobisimidazole (B═NR) of structure:

wherein N is a nitrogen atom and R is hydrogen or a substituted orunsubstituted alkyl or aryl attached to N, preferably wherein R is H.The average number of repeat units of the polymer chains is typically inthe range of from about from about 10 to about 25,000, more typically inthe range of from about 100 to 1,000, even more typically in the rangeof from about 125 to 500, and further typically in the range of fromabout 150 to 300.

As used herein, filaments of the present invention are prepared frompolybenzazole (PBZ) or polypyridazole polymers. For purposes herein, theterm “filament” or “fiber” refers to a relatively flexible,macroscopically homogeneous body having a high ratio of length to widthacross its cross-sectional area perpendicular to its length. Thefilament cross section may be any shape, but is typically circular.

As herein defined, “yarn” refers to a continuous length of two or morefibers, wherein fiber is as defined hereinabove.

For purposes herein, “fabric” refers to any woven, knitted, or non-wovenstructure. By “woven” is meant any fabric weave, such as, plain weave,crowfoot weave, basket weave, satin weave, twill weave, and the like. By“knitted” is meant a structure produced by interlooping or intermeshingone or more ends, fibers or multifilament yarns. By “non-woven” is meanta network of fibers, including unidirectional fibers, felt, and thelike.

In some embodiments, the more preferred rigid rod polypyridazolesinclude, but are not limited to polypyridobisimidazole homopolymers andcopolymers such as those described in U.S. Pat. No. 5,674,969 (toSikkema, et al. on Oct. 7, 1997). One such exemplarypolypyridobisimidazole is homopolymer poly(1,4-(2,5-dihydroxy)phenylene-2,6-diimidazo[4,5-b:4′5′-e]pyridinylene). This polymer is alsoknown using various terminology, for example:poly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole);poly[(1,4-dihydroxyimidazo[4,5-b:4′,5′-e]pyridine-2,6-diyl)(2,5-dihydroxy-1,4-phenylene)];poly[(2,6-diimidazo[4,5-b:4′,5′-e]pyridinylene-(2,5-dihydroxy-1,4-phenylene)];Chemical Abstracts Registry No. 167304-74-7,poly[(1,4-dihydrodiimidazo[4,5-b:4′,5′-e]pyridine-2,6-diyl)(2,5-dihydroxy-1,4-phenylene)];2,5-dihydroxyterephthalic acid-1,2,4,5-tetraminopyridine copolymer;PIPD; pyridobisimidazole-2,6-diyl (2,5-dihydroxy-p-phenylene) copolymer;poly(1,4-(2,5-dihydroxy)phenylene-2,6-diimidazo[4,5-b:4′,5′-e]pyridinylene);andpoly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d5,6-d′]bisimidazole).

The polyareneazole polymers used in this invention may have theproperties associated with a rigid-rod structure, a semi-rigid-rodstructure, or a flexible coil structure; preferably a rigid rodstructure. When this class of rigid rod polymers has structure (b1) or(b2) it preferably has two azole groups fused to the aromatic group Ar¹.

Suitable polyareneazoles useful in this invention include homopolymersand copolymers. Up to as much as about 25 percent, by weight, of otherpolymeric material can be blended with the polyareneazole. Alsocopolymers may be used having as much as about 25 percent or more ofother polyareneazole monomers or other monomers substituted for amonomer of the majority polyareneazole. Suitable polyareneazolehomopolymers and copolymers can be made by known procedures, such asthose described in U.S. Pat. Nos. 4,533,693 (to Wolfe et al. on Aug. 6,1985), 4,703,103 (to Wolfe et al. on Oct. 27, 1987), 5,089,591 (toGregory et al. on Feb. 18, 1992), 4,772,678 (Sybert et al. on Sep. 20,1988), 4,847,350 (to Harris et al. on Aug. 11, 1992), 5,276,128 (toRosenberg et al. on Jan. 4, 1994) and U.S. Pat. No. 5,674,969 (toSikkema, et al. on Oct. 7, 1997), the entirety of each is incorporatedby reference herein. Additives may also be incorporated in thepolyareneazole in desired amounts, such as, for example, anti-oxidants,lubricants, ultra-violet screening agents, colorants and the like.

When any variable occurs more than one time in any constituent or in anyformula, its definition in each occurrence is independent of itsdefinition at every other occurrence. Combinations of substituentsand/or variables are permissible only if such combinations result instable compounds.

Several embodiments of the present invention are directed topolyareneazole filaments, more specifically to polybenzazole (PBZ)filaments or polypyridazole filaments, and processes for the preparationof such filaments. Other embodiments further include yarns, fabrics, andarticles incorporating filaments of this invention, and processes formaking such yarns, fabrics, and articles.

Filaments of the present invention are prepared from polybenzazole (PBZ)or polypyridazole polymers. For purposes herein, the term “filament”refers to a relatively flexible, macroscopically homogeneous body havinga high ratio of length to width across its cross-sectional areaperpendicular to its length. The filament cross section may be anyshape, but is typically circular. Herein, the term “filament” is usedinterchangeably with the term “fiber”.

Suitable polyareneazole monomers are reacted in a solution ofnon-oxidizing and dehydrating acid under non-oxidizing atmosphere withmixing at a temperature that is increased in step-wise or rampedfashion. The polyareneazole polymer can be rigid rod, semi-rigid rod orflexible coil. It is preferably a lyotropic liquid-crystalline polymer,which forms liquid-crystalline domains in solution when itsconcentration exceeds a critical concentration.

In certain embodiments of the present invention, there are providedprocesses for increasing the inherent viscosity of a polyareneazolepolymer solution. These processes typically include the steps ofcontacting, in polyphosphoric acid, azole-forming monomers and ironmetal powder, the iron metal powder added in an amount of from about0.05 to about 0.9 weight percent, based on the total weight of theazole-forming monomers, and reacting the azole-forming monomers to formthe polyareneazole polymer. The azole-forming monomers are suitablyprepared separately in aqueous solutions and precipitated to form amonomer complex in a reaction vessel. For example, one suitable processuses a vessel under a nitrogen purge that is charged with a phosphoricacid buffer (pH in the range of from about 4.0 to about 4.5) and water.The solution is heated to approximately 50° C. In a second vessel undera nitrogen purge, an aqueous azole-forming monomer solution is made,preferably 2,5-dihydroxy terephthalic acid (“DHTA”), by combining analkaline salt of 2,5-dihydroxy terephthalic acid, Na₂S₂O₄, NH₄OH, andwater. In a third vessel, an aqueous mixture of a second azole-formingmonomer that is capable of reacting with the first azole-forming monomeris prepared, preferably tetraminopyridine (“TAP”)-3HCl—H₂O solution ismade by combining TAP-3HCl—H₂O and water in a vessel under a nitrogenblanket, and then adding some NH₄OH.

The solution of the third vessel is transferred to the second vessel,and the pH is adjusted to within the range of from about 9 to about 10in some embodiments. The combined solution is then warmed toapproximately 50° C. while stirring with nitrogen bubbling until thesolution clears. The cleared solution is transferred to the first vesselwith enough additional H₃PO₄ to maintain the pH to about 4.5 during theaddition process to precipitate the monomer complex to form a slurry.The slurry containing the monomer complex is typically filtered undernitrogen and washed with water and degassed ethanol. The monomer complexcan be kept in an inert atmosphere and dried prior to polymerization.

A more preferred process for increasing the inherent viscosity of apolyareneazole polymer solution includes combining in an autoclave,2,6-diamino-3,5-dinitropyridine (“DADNP”), water, 5% Pt/C catalyst andammonium hydroxide and heating under pressure to hydrogenate the DADNP.After venting and cooling, activated carbon in water is added as aslurry to the autoclave and mixed. The solution is then filtered,forming a colorless TAP solution. This is added to a K₂-DHTA/Na₂S₂O₄solution with mixing. A pre-mixed phosphate buffer solution is dilutedwith water and precharged in a coupling vessel and heated to about 50°C. while mixing. The basic TAP/K₂-DHTA mixture (pH about 10) is thenadded to the coupling vessel while adding aqueous H₃PO₄ to control thepH around 4.5. Large amounts of fine light-yellow monomer complexcrystals form during the addition. The final pH is brought to about 4.5while the monomer complex slurry is cooled. The slurry is then filteredto give a pale yellow cake. The monomer complex cake is washed withwater followed by ethanol before being set to purge with nitrogenovernight. The color of the final cake is pale yellow.

Polymerization of the monomer complex is typically carried out in areactor suitably equipped with connections for purging with inert gas,applying a vacuum, heating and stirring. Monomer complex, P₂O₅, PPA andpowdered metal are typically added to the reactor. The reactor istypically purged, heated and mixed to effect polymerization. In oneparticularly preferred embodiment, about 20 parts of monomer complex,about 10 parts of P₂O₅, about 60 parts of polyphosphoric acid and about0.1 parts tin or iron metal are added to a suitable reactor. Thecontents of the reactor are stirred at about 60 rpm and heated to about100° C. for about one hour under vacuum with a slight nitrogen purge.The temperature is typically raised to at least 120° C., preferably toat least about 130° C., and preferably no more than about 140° C. for afew more hours, preferably about four hours. The temperature is thenraised and held at a higher temperature, at least about 150° C., moretypically at least about 170° C., and preferably at about 180° C. forabout an hour, more preferably for about two hours. The reactor istypically flushed with nitrogen and a sample of the polymer solution istaken for viscosity determination.

The relative molecular weights of the polyareneazole polymers aresuitably characterized by diluting the polymer products with a suitablesolvent, such as methane sulfonic acid, to a polymer concentration of0.05 g/dl, and measuring one or more dilute solution viscosity values at30° C. Molecular weight development of polyareneazole polymers of thepresent invention is suitably monitored by, and correlated to, one ormore dilute solution viscosity measurements. Accordingly, dilutesolution measurements of the relative viscosity (“V_(rel)” or “η_(rel)”or “η_(rel)”) and inherent viscosity (“V_(inh)” or “η_(inh)” or“n_(inh)”) are typically used for monitoring polymer molecular weight.The relative and inherent viscosities of dilute polymer solutions arerelated according to the expressionV _(inh)=ln(V _(rel))/C,where ln is the natural logarithm function and C is the concentration ofthe polymer solution. V_(rel) is a unitless ratio of the polymersolution viscosity to that of the solvent free of polymer, thus V_(inh)is expressed in units of inverse concentration, typically as decilitersper gram (“dl/g”). Accordingly, in certain aspects of the presentinvention the polyareneazole polymers are produced that arecharacterized as providing a polymer solution having an inherentviscosity of at least about 22 dl/g at 30° C. at a polymer concentrationof 0.05 g/dl in methane sulfonic acid. Because the higher molecularweight polymers that result from the invention disclosed herein giverise to viscous polymer solutions, a concentration of about 0.05 g/dlpolymer in methane sulfonic acid is useful for measuring inherentviscosities in a reasonable amount of time.

Various amounts and types of metal powders are useful for helping tobuild the molecular weight of polyareneazoles. In certain processes itis particularly preferred to use iron metal powder present in an amountof from about 0.1 to about 0.5 weight percent based on monomer. Suitableiron metal powder will be particularly fine to provide sufficientsurface area for catalyzing the polymerization reaction. In this regard,iron metal powder will suitably have a particle size that will passthrough a 200 mesh screen.

The azole-forming monomers suitably include 2,5-dimercapto-p-phenylenediamine, terephthalic acid, bis-(4-benzoic acid), oxy-bis-(4-benzoicacid), 2,5-dihydroxyterephthalic acid, isophthalic acid,2,5-pyridodicarboxylic acid, 2,6-napthalenedicarboxylic acid,2,6-quinolinedicarboxylic acid, 2,6-bis(4-carboxyphenyl)pyridobisimidazole, 2,3,5,6-tetraminopyridine, 4,6-diaminoresorcinol,2,5-diaminohydroquinone, 1,4-diamino-2,5-dithiobenzene, or anycombination thereof. Preferably, the azole-forming monomers include2,3,5,6-tetraminopyridine and 2,5-dihydroxyterephthalic acid. In certainembodiments, it is preferred that that the azole-forming monomers arephosphorylated. Preferably, phosphorylated azole-forming monomers arepolymerized in the presence of polyphosphoric acid and a metal catalyst.

Azole-forming monomers can be selected for generating any of a number ofpolyareneazoles, and suitable polyareneazoles made according to certainembodiments of the processes of the present invention includepolypyridoazoles, which preferably include polypyridobisimidazoles,which preferably includepoly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole).

Monomers are selected for generating any of a number of polyareneazoles,and suitable polyareneazoles made according to certain embodiments ofthe processes of the present invention will include a polybenzazole,which preferably includes a polybenzabisoxazole.

In several embodiments, the present invention also provides processesfor increasing the inherent viscosity of a polyareneazole polymer. Theseprocesses suitably include the steps of contacting, in polyphosphoricacid, azole-forming monomers and a metal powder including vanadiummetal, chromium metal, or any combination thereof, the metal powderadded in an amount of from about 0.05 to about 0.9 weight percent, basedon the total amount of azole-forming monomers, and reacting the monomersto form the polyareneazole polymer. Typically, these processes suitablyform polyareneazoles that are characterized as providing a polymersolution having an inherent viscosity of at least about 22 dl/g at 30°C. at a polymer concentration of 0.05 g/dl in methane sulfonic acid. Incertain embodiments, the metal powder is present in an amount of about0.1 to about 0.5 weight percent based on monomer. Suitable metal powdershave a fine particle size that provide a high surface area for effectingcatalysis of the polymerization reaction. Accordingly, suitable metalpowders have a particle size such that will pass through a 200 meshscreen. Similar monomers can be polymerized according to these processesto form polymers are provided using these processes as described above.

Several embodiments are also directed to processes for preparing apolyareneazole polymer that include contacting, in polyphosphoric acid,azole-forming monomer complex and tin metal powder, the azole-formingmonomer complex synthesized using a molar excess of a firstazole-forming monomer to a second azole-forming monomer, the tin metalpowder added in an amount of from about 0.05 to about 0.9 weightpercent, based on the total amount of azole-forming monomer complex, andreacting the monomer complex to form the polyareneazole polymer.Typically, these processes suitably form polyareneazoles that arecharacterized as providing a polymer solution having an inherentviscosity of at least about 22 dl/g at 30° C. at a polymer concentrationof 0.05 g/dl in methane sulfonic acid. In certain embodiments, the metalpowder is present in an amount of about 0.1 to about 0.5 weight percentbased on monomer. Suitable metal powders have a fine particle size thatprovides a high surface area for effecting catalysis of thepolymerization reaction. Accordingly, suitable metal powders have aparticle size such that will pass through a 200 mesh screen. Similarmonomers can be polymerized according to these processes to formpolymers are provided using these processes as described above.

Processes for making a monomer complex comprising 2,3,5,6-tetraminopyridine and 2,5-dihydroxy terephthalic acid monomers are also provided.In these embodiments, the processes typically include the steps ofcontacting a molar excess of a 2,3,5,6-tetraminopyridine free base inwater to a 2,5-dihydroxy terephthalic acid dipotassium salt to form anaqueous mixture, and adjusting the pH of the aqueous mixture to withinthe range of from about 3 to about 5 to precipitate the monomer complex.More typically, in certain embodiments, the molar ratio of the2,3,5,6-tetraminopyridine free base to the 2,5-dihydroxy terephthalicacid dipotassium salt is at least about 1.05 to 1, even more typicallyat least about 1.075 to 1, and particularly at least about 1.15 to 1.

The pH of the reaction mixtures are suitably maintained by adding anacid, preferably orthophosphoric acid, to the aqueous mixture. Invarious embodiments, suitable salts include an alkaline salt of the2,5-dihydroxy terephthalic acid salt and an ammonium salt of2,5-dihydroxy terephthalic acid. Preferably, the alkaline salt of the2,5-dihydroxy terephthalic acid is 2,5-dihydroxy terephthalic aciddipotassium salt.

The pH of the aqueous mixture is typically adjusted to precipitate themonomer complex. A suitable pH for precipitating the monomer complex isin the range of from about 4.3 to about 4.6. After the monomer complexis formed, certain embodiments of the present invention also include oneor more additional steps of polymerizing the monomer complex to form apolyareneazole. In these embodiments, any of the monomers as describedherein can be used for forming any of the polyareneazoles. For example,in certain embodiments, the polyareneazole,poly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole),is formed using a monomer complex composed of 2,3,5,6-tetramino pyridineand 2,5-dihydroxy terephthalic acid monomers.

Several embodiments also provide processes for making a monomer complexcomposed of 2,3,5,6-tetramino pyridine and 2,5-dihydroxy terephthalicacid monomers. These processes include the steps of contacting2,3,5,6-tetraminopyridine free base in water with 2,5-dihydroxyterephthalic acid dipotassium salt to form an aqueous mixture, andadjusting the pH of the aqueous mixture to within the range of fromabout 3 to about 5 to precipitate the monomer complex. In theseembodiments, almost any molar ratio of the 2,3,5,6-tetraminopyridinefree base to the 2,5-dihydroxy terephthalic acid dipotassium salt can beused, for example, a 1 to 1 molar ratio of 2,5-dihydroxy terephthalicacid sodium salt to a 2,3,5,6-tetraminopyridine free base can be used toprepare the complex. Typically, the molar ratio of the2,3,5,6-tetraminopyridine free base to the 2,5-dihydroxy terephthalicacid dipotassium salt is at least about 1 to 1, more typically at leastabout 1.05 to 1, even more typically at least about 1.075 to 1, andfurther typically at least about 1.15 to 1. The pH is suitably adjustedby adding a dilute acid, preferably orthophosphoric acid, to the aqueousmixture. In certain preferred embodiments, the pH of the aqueous mixtureis adjusted to within a range of from about 4.3 to about 4.6 toprecipitate the monomer complex.

Poly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole)polymers are also provided in several embodiments. These polymers arecharacterized as providing a polymer solution with methane sulfonic acidhaving an inherent viscosity of at least about 22 dl/g, more typicallyat least about 25 dl/g, even more typically at least about 28 dl/g, andfurther typically at least about 30 dl/g, at 30° C. at a polymerconcentration of 0.05 g/dl. Various embodiments of the present inventionalso include filaments that can be prepared from thesepoly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole)polymers. For example, polymer dope solutions can be extruded or spunthrough a die or spinneret to prepare or spin a dope filament. Thespinneret preferably contains a plurality of holes. The number of holesin the spinneret and their arrangement is not critical to the invention,but it is desirable to maximize the number of holes for economicreasons. The spinneret can contain as many as 100 or 1000, or more, andthey may be arranged in circles, grids, or in any other desiredarrangement. The spinneret may be constructed out of any materials thatwill not be degraded by the dope solution. In various embodiments,multifilament yarns comprising a plurality of filaments are alsoprovided. The number of filaments per multifilament yarn isapproximately the number of holes in the spinneret. Typically, themultifilament yarns prepared with filaments of the present inventionhave a yarn tenacity of at least about 24 grams per denier (“gpd”).

Additional processes for preparingpoly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole)polymers are also provided. These embodiments include contacting a molarexcess of a 2,3,5,6-tetramino pyridine free base in water to a2,5-dihydroxy terephthalic acid salt to form an aqueous mixture,adjusting the pH of the aqueous mixture to within the range of fromabout 3 to about 5 to precipitate a monomer complex composed of2,3,5,6-tetramino pyridine and 2,5-dihydroxy terephthalic acid monomers,contacting, in polyphosphoric acid, the monomer complex with metalpowder, the metal powder added in an amount of from about 0.05 to about0.9 weight percent, based on the total weight of the monomer complex,and polymerizing the monomer complex in polyphosphoric acid to form thepolymer solution. In certain of these embodiments, the molar ratio of2,3,5,6-tetramino pyridine to 2,5-dihydroxy terephthalic acid typicallyis at least about 1.05 to 1, more typically at least about 1.075 to 1,and even more typically at least about 1.15 to 1. In certain of theseembodiments, the pH is suitably adjusted by adding an acid, such asorthophosphoric acid, to the aqueous mixture. Suitably, thepolyphosphoric acid has an equivalent P₂O₅ content after polymerizationof typically at least about 81 percent, and more typically at leastabout 82 percent. The metal powder suitably includes iron powder, tinpowder, vanadium powder, chromium powder, or any combination thereof.Preferably, the metal powder is iron powder. In certain of theseembodiments, the 2,5-dihydroxy terephthalic acid salt is an alkalinesalt or an ammonium salt of 2,5-dihydroxy terephthalic acid, andpreferably the alkaline salt is 2,5-dihydroxy terephthalic aciddipotassium salt. In additional embodiments, the processes may furtherinclude one or more additional steps for preparing articles ofmanufacture, such as filaments and yarns. Thus, the present inventionalso provides the additional step of forming fibers from polymersolutions (i.e., dopes) ofpoly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole)in polyphosphoric acid using one or fiber spinning processes.Preferably,poly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole)polymer solutions have an inherent viscosity measured in 0.05 g/dlmethane sulfonic acid of at least about 22 dl/g when measured in 0.05g/dl methane sulfonic acid at 30° C.

There are also provided processes for preparing apoly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole)that include the steps of contacting 2,3,5,6-tetramino pyridine freebase in water with 2,5-dihydroxy terephthalic acid dipotassium salt toform an aqueous mixture, adjusting the pH of the aqueous mixture towithin the range of from about 3 to about 5 to precipitate a monomercomplex composed of 2,3,5,6-tetramino pyridine and 2,5-dihydroxyterephthalic acid monomers, contacting, in polyphosphoric acid, themonomer complex with metal powder, the metal powder added in an amountof from about 0.05 to about 0.9 weight percent, based on the totalweight of the monomers, and polymerizing the monomers in polyphosphoricacid to form the polymer solution. In certain of these embodiments, themolar ratio of the 2,3,5,6-tetramino pyridine to the 2,5-dihydroxyterephthalic acid is typically at least about 1 to 1, more typically atleast about 1.05 to 1, even more typically at least about 1.075 to 1,and further typically at least about 1.15 to 1. The pH is adjusted incertain of these embodiments by adding a suitable acid, preferablyorthophosphoric acid, to the aqueous mixture. In certain embodiments,the reaction mixture preferably includes polyphosphoric acid having anequivalent P₂O₅ content of at least about 81 percent afterpolymerization, and more preferably at least about 82 percent afterpolymerization. In various embodiments, the metal powder typicallyincludes iron powder, tin powder, vanadium powder, chromium powder, orany combination thereof. Preferably, the metal powder is iron powder.Certain embodiments further include at least one additional step offorming a fiber from the polymer solution. Suitable polymer solutionsthat are spinnable into filaments and multifilament yarn typicallyincludepoly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole)having an inherent viscosity of at least about 22 dl/g when measured in0.05 g/dl methane sulfonic acid at 30° C.

Certain embodiments of the present invention are discussed in referenceto FIG. 1. In some embodiments, the polymer is formed in acid solventproviding the dope solution 2. In other embodiments, the polymer isdissolved in the acid solvent after formation. Either is within theambit of the invention. Preferably the polymer is formed in acid solventand provided for use in the invention. The dope solution 2, comprisingpolymer and polyphosphoric acid, typically contains a high enoughconcentration of polymer for the polymer to form an acceptable filament6 after extrusion and coagulation. When the polymer is lyotropicliquid-crystalline, the concentration of polymer in the dope 2 ispreferably high enough to provide a liquid-crystalline dope. Theconcentration of the polymer is preferably at least about 7 weightpercent, more preferably at least about 10 weight percent and mostpreferably at least about 14 weight percent. The maximum concentrationis typically selected primarily by practical factors, such as polymersolubility and dope viscosity. The concentration of polymer ispreferably no more than 30 weight percent, and more preferably no morethan about 20 weight percent.

The polymer dope solution 2 may contain additives such as anti-oxidants,lubricants, ultra-violet screening agents, colorants and the like whichare commonly incorporated.

The polymer dope solution 2 is typically extruded or spun through a dieor spinneret 4 to prepare or spin the dope filament 6. The spinneret 4preferably contains a plurality of holes. The number of holes in thespinneret and their arrangement is not critical to the invention, but itis desirable to maximize the number of holes for economic reasons. Thespinneret 4 can contain as many as 100 or 1000, or more, and they may bearranged in circles, grids, or in any other desired arrangement. Thespinneret 4 may be constructed out of any materials that will not bedegraded by the dope solution 2.

Fibers may be spun from solution using any number of processes, however,wet spinning and “air-gap” spinning are the best known. The generalarrangement of the spinnerets and baths for these spinning processes iswell known in the art, with the figures in U.S. Pat. Nos. 3,227,793;3,414,645; 3,767,756; and 5,667,743 being illustrative of such spinningprocesses for high strength polymers, the entirety of each isincorporated by reference herein. In “air-gap” spinning the spinnerettypically extrudes the fiber first into a gas, such as air. Using FIG. 1to help illustrate a process employing “air-gap spinning (also sometimesknown as “dry-jet” wet spinning), dope solution 2 exiting the spinneret4 enters a gap 8 (typically called an “air gap” although it need notcontain air) between the spinneret 4 and a coagulation bath 10 for avery short duration of time. The gap 8 may contain any fluid that doesnot induce coagulation or react adversely with the dope, such as air,nitrogen, argon, helium, or carbon dioxide. The dope filament 6 is drawnacross the air gap 8, with or without stretching and immediatelyintroduced into a liquid coagulation bath. Alternately, the fiber may be“wet-spun”. In wet spinning, the spinneret typically extrudes the fiberdirectly into the liquid of a coagulation bath and normally thespinneret is immersed or positioned beneath the surface of thecoagulation bath. Either spinning process may be used to provide fibersfor use in the processes of the invention. In some embodiments of thepresent invention, air-gap spinning is preferred.

The filament 6 is “coagulated” in the coagulation bath 10 containingwater or a mixture of water and phosphoric acid, which removes enough ofthe polyphosphoric acid to prevent substantial stretching of thefilament 6 during any subsequent processing. If multiple fibers areextruded simultaneously, they may be combined into a multifilament yarnbefore, during or after the coagulation step. The term “coagulation” asused herein does not necessarily imply that the dope filament 6 is aflowing liquid and changes into a solid phase. The dope filament 6 canbe at a temperature low enough so that it is essentially non-flowingbefore entering the coagulation bath 10. However, the coagulation bath10 does ensure or complete the coagulation of the filament, i.e., theconversion of the polymer from a dope solution 2 to a substantiallysolid polymer filament 12. The amount of solvent, i.e., polyphosphoricacid, removed during the coagulation step will depend on the residencetime of the filament 6 in the coagulation bath, the temperature of thebath 10, and the concentration of solvent therein. For example, using a20 weight percent solution of phosphoric acid at a temperature of about23° C., a residence time of about one second will remove about 70percent of the solvent present in the filament 6.

The residual polyphosphoric acid associated with the filament istypically substantially hydrolyzed and removed to preserve polymer fiberproperties. PPA is conveniently hydrolyzed by heating the filament oryarn prior to washing and/or neutralization steps. One manner ofhydrolysis includes convective heating of the coagulated fiber for ashort period of time. As an alternative to convective heating, thehydrolysis may be effected by heating the wet, as coagulated filament oryarn in boiling water or an aqueous acid solution. This treatmentprovides PPA hydrolysis while adequately retaining the tensile strengthof the product fiber. The heat treatment step may occur in a separatecabinet 14, or as an initial process sequence followed by one or moresubsequent washing steps in an existing washing cabinet 14. In someembodiments, this is solved by (a) contacting the dope filament with asolution in bath or cabinet 14 thereby hydrolyzing PPA and then (b)contacting the filament with a neutralization solution in bath orcabinet 16 containing water and an effective amount of a base underconditions sufficient to neutralize sufficient quantities of thephosphoric acid, polyphosphoric acid, or any combination thereof in thefilament.

After treatment to substantially hydrolyze PPA associated with thecoagulated filament, hydrolyzed PPA may be removed from the filament oryarn 12 by washing in one or more washing steps to remove most of theresidual acid solvent/and or hydrolyzed PPA from the filament or yarn12. The washing of the filament or yarn 12 may be carried out bytreating the filament or yarn 12 with a base, or with multiple washingswhere the treatment of the filament or yarn with base is preceded and/orfollowed by washings with water. The filament or yarn may also betreated subsequently with an acid to reduce the level of cations in thepolymer. This sequence of washings may be carried out in a continuousprocess by running the filament through a series of baths and/or throughone or more washing cabinets. FIG. 1 depicts one washing bath or cabinet14. Washing cabinets typically comprise an enclosed cabinet containingone or more rolls which the filament travels around a number of times,and across, prior to exiting the cabinet. As the filament or yarn 12travels around the roll, it is sprayed with a washing fluid. The washingfluid is continuously collected in the bottom of the cabinet and drainedtherefrom.

The temperature of the washing fluid(s) is preferably greater than 30°C. The washing fluid may also be applied in vapor form (steam), but ismore conveniently used in liquid form. Preferably, a number of washingbaths or cabinets are used. The residence time of the filament or yarn12 in any one washing bath or cabinet 14 will depend on the desiredconcentration of residual phosphorus in the filament or yarn 12, butpreferably the residence time are in the range of from about one secondto less than about two minutes. In a continuous process, the duration ofthe entire washing process in the preferred multiple washing bath(s)and/or cabinet(s) is preferably no greater than about 10 minutes, morepreferably more than about 5 seconds and no greater than about 160seconds.

In some embodiments, preferred bases for the removal of hydrolyzed PPAinclude NaOH; KOH; Na₂CO₃; NaHCO₃; K₂CO₃; KHCO₃; or trialkylamines,preferably tributylamine; or mixtures thereof. In one embodiment, thebase is water soluble.

After treating the fiber with base, the process optionally may includethe step of contacting the filament with a washing solution containingwater or an acid to remove all or substantially all excess base. Thiswashing solution can be applied in a washing bath or cabinet 18.

The fiber or yarn 12 may be dried in a dryer 20 to remove water andother liquids. The temperature in the dryer is typically about 80° C. toabout 130° C. The dryer residence time is typically 5 seconds to perhapsas much as 5 minutes at lower temperatures. The dryer can be providedwith a nitrogen or other non-reactive atmosphere. Then the fiber canoptionally be further processed in, for instance, a heat setting device22. Further processing may be done in a nitrogen purged tube furnace 22for increasing tenacity and/or relieving the mechanical strain of themolecules in the filaments. Finally, the filament or yarn 12 is wound upinto a package on a windup device 24. Rolls, pins, guides, and/ormotorized devices 26 are suitably positioned to transport the filamentor yarn through the process.

Preferably, the phosphorous content of the dried filaments after removalof the hydrolyzed PPA is less than about 5,000 ppm (0.5%) by weight, andmore preferably, less than about 4,000 ppm (0.4%) by weight, and mostpreferably less than about 2,000 ppm (0.2%) by weight.

The invention is further directed, in part, to a yarn comprising aplurality of the filaments of the present invention, fabrics thatinclude filaments or yarns of the present invention, and articles thatinclude fabrics of the present invention. For purposes herein, “fabric”means any woven, knitted, or non-woven structure. By “woven” is meantany fabric weave, such as, plain weave, crowfoot weave, basket weave,satin weave, twill weave, and the like. By “knitted” is meant astructure produced by interlooping or intermeshing one or more ends,fibers or multifilament yarns. By “non-woven” is meant a network offibers, including unidirectional fibers (if contained within a matrixresin), felt, and the like.

EXAMPLES

As used herein, the terms “mmole” and “millimole” are synonymous. Allpolymer solids concentrations, weight percents based on monomer, andpolymer solution percent P₂O₅ concentrations are expressed on the basisof TD-complex as a 1:1 molar complex between TAP and DHTA. TheTD-complex is believed to be a monohydrate.

The test methods described below were used in the following Examples.

Temperature: measured in degrees Celsius (° C.).

Denier: determined according to ASTM D 1577 and is the linear density ofa fiber as expressed as weight in grams of 9000 meters of fiber.

Tenacity: determined according to ASTM D 3822 and is the maximum orbreaking stress of a fiber as expressed as force per unitcross-sectional area.

Elemental Analysis: Elemental analysis of alkaline cation (M) andphosphorus (P) is determined according to the inductively coupled plasma(ICP) method as follows. A sample (1-2 grams), accurately weighed, isplaced into a quartz vessel of a CEM Star 6 microwave system.Concentrated sulfuric acid (5 ml) is added and swirled to wet. Acondenser is connected to the vessel and the sample is digested usingthe moderate char method. This method involves heating the sample tovarious temperatures up to about 260° C. to char the organic material.Aliquots of nitric acid are automatically added by the instrument atvarious stages of the digestion. The clear, liquid final digestate iscooled to room temperature and diluted to 50 ml with deionized water.The solution may be analyzed on a Perkin Elmer optima inductivelycoupled plasma device using the manufacturers' recommended conditionsand settings. A total of twenty-six different elements may be analyzedat several different wavelengths per sample. A 1/10 dilution may berequired for certain elements such as sodium and phosphorus. Calibrationstandards are from 1 to 10 ppm.

Many of the following examples are given to illustrate variousembodiments of the invention and should not be interpreted as limitingit in any way. All parts and percentages are by weight unless otherwiseindicated.

Monomer Complex Examples Example 1

This example illustrates the use of 5 percent molar excess of2,3,5,6-tetraminopyridine (“TAP”) in the making of monomer complex by abatch process. Water was degassed and deionized.

A first stirred 2-liter resin kettle under a nitrogen purge was chargedwith 50 ml of 85% H₃PO₄ and 450 ml water, followed by the addition of a10 percent by weight sodium hydroxide solution until the pH of thematerial in the kettle was approximately 4.6 as measured by a pH probe.The solution was heated to approximately 50° C.

In a second stirred 2-liter resin kettle under a nitrogen purge, a2,5-dihydroxy terephthalic acid (“DHTA”) solution was made by combining41.1 g of a dipotassium salt of 2,5-dihydroxy terephthalic acid(“K₂-DHTA”), 1 g Na₂S₂O₄, 60 g NH₄OH, and 700 g water. The K₂-DHTA andNa₂S₂O₄ were weighed in a glove box first.

A TAP-3HCl—H₂O solution was made by combining 700 g water and 42 gTAP-3HCl.H₂O in a quart bottle equipped with a septum (under a nitrogenblanket). 60 g of NH₄OH were then added. This solution was cannulated tothe second resin kettle. This combined solution in the second kettle hada pH of approximately 9 to 10. The combined solution was warmed toapproximately 50° C. while stirring with nitrogen bubbling until thesolution became clear. This solution was cannulated to the first resinkettle along with enough additional H₃PO₄ to adjust the pH to 4.5 toprecipitate the monomer complex to form a slurry. The H₃PO₄ solution wasmade by diluting 50 ml of 85% H₃PO₄ in 500 ml water.

The slurry containing the monomer complex was filtered under nitrogenand washed twice with 200 ml of water (6-8 grams water per gram of wetproduct slurry) and with 10 ml degassed ethanol (˜1 gram ethanol pergram of wet product). The monomer complex was kept under nitrogen anddried by steam heating overnight, and recovered in a nitrogen atmosphereglove box.

Polymerization (Example With 5.0% molar excess TAP in Monomer ComplexFormation). Into a clean dry 200 ml glass tubular reactor having aninside diameter of 4.8 cm and that was equipped with the necessaryconnections for purging nitrogen and applying a vacuum, and around whicha heating jacket was arranged and which further contained double helixshaped basket stirrer were charged with 23.00 g of monomer complex,11.24 g of P₂O₅, 66.29 g of polyphosphoric acid (“PPA”) with a % P₂O₅equivalent to 85.15%, and 0.115 g Sn. The contents were stirred at 60rpm and heated to 100° C. for one hour under vacuum with a slightnitrogen purge. The temperature was raised and held at 137° C. for 4hours. The temperature was raised and held at 180° C. for 2 hours. Thereactor was flushed with nitrogen. a sample of the polymer solution wasdiluted with methane sulfonic acid to 0.05% concentration, and theinherent viscosity was measured at 30° C. to be n_(inh)=23 dl/g.

Example 2

The procedure of Example 1 was repeated, however 43 grams of TAP wereused to make the TAP.3HCl.H₂O solution, providing a molar excess of 7.5%TAP as compared to a molar excess of 5% TAP as in Example 1.

Polymerization (Example With 7.5% molar excess TAP in Monomer ComplexFormation). Into a clean dry 200 ml glass tubular reactor having aninside diameter of 4.8 cm, equipped with the necessary connections forpurging nitrogen and applying a vacuum, and around which a heatingjacket was arranged and which further contained double helix shapedbasket stirrer, was charged 20.00 g of monomer complex, 7.78 g of P₂O₅,59.52 g of PPA with a % P₂O₅ equivalent to 85.65%, and 0.115 g Sn. Thestirrer was turned on at 100 rpm and the contents were heated to 100° C.for one hour under vacuum with a slight N₂ purge. The temperature wasraised and held at 137° C. for 3 hours. The temperature was raised andheld at 180° C. for 2 hours. The reactor was flushed with nitrogen gas(“N₂”) and a sample of the polymer solution was diluted with methanesulfonic acid to 0.05% concentration. The n_(inh)=28.5 dl/g.

Example 3

The procedure of Example 1 was repeated, however 46 grams of TAP wereused to make the TAP.3HCl.H₂O solution, providing a molar excess of 15%TAP compared to a 5% molar excess as in Example 1.

Polymerization (Example With 15% molar excess TAP in Monomer ComplexFormation). Into a clean dry 200 ml glass tubular reactor having aninside diameter of 4.8 cm, equipped with the necessary connections forpurging nitrogen and applying a vacuum, and around which a heatingjacket was arranged and which further contained double helix shapedbasket stirrer was charged 20.00 of monomer complex, 7.79 g of P₂O₅,59.54 g of PPA with a P₂O₅ equivalent to 85.65%, and 0.115 g Sn. Thecontents were stirred at 100 rpm and heated to 100° C. for one hourunder vacuum with a slight N₂ purge. The temperature was raised to 137°C. held there for 4 hours. The temperature was raised and held at 180°C. for 2 hours. The reactor was flushed with N₂ and a sample of thepolymer solution was diluted with methane sulfonic acid to 0.05%concentration. The n_(inh)=33.4 dl/g.

Example 4

This example illustrates the use of 7.5 percent molar excess of2,3,5,6-tetraminopyridine (TAP) in the making of monomer complex by adirectly coupled process. A dipotassium salt of 2,5-dihydroxyterephthalic acid (K₂-DHTA/Na₂S₂O₄) solution was prepared in a vessel bycombining 126.81 grams of K₂-DHTA, 2208 grams of water, and 2.2 gramssodium dithionate.

In an autoclave, 100.3 grams of 2,6-diamino-3,5-dinitropyridine (DADNP),508 grams water, 2.04 gram 5% Pt/C catalyst (using 1 gram of catalystper dry basis) and 10 grams of ammonium hydroxide were combined andheated at 65° C. at 500 psig. Hydrogenation of the DADNP was complete in2 hours. After venting and cooling to 30° C., about 15 g of Darco G60activated carbon in 100 g water was added as a slurry to the clave andmixed for 1 hour. The solution was filtered to remove the catalystfollowed by a single CUNO Biocap 30 54SP filter. The filtration took 30minutes and the color of the filtered solution was clear throughout thetransfer.

The colorless TAP solution was added to the K₂-DHTA/Na₂S₂O₄ solutionwith mixing at 50° C. The color of the K₂-DHTA/Na₂S₂O₄ solution waslight yellow and did not change during the TAP addition the pH of theTAP/K₂-DHTA mixture was 10.0. The clave and filters were then rinsedwith 100 g H₂O which was added to the vessel. The theoretical amount ofTAP, including DADNP purity (98%) that could have been made, filtered,and transferred to the mix vessel was 68.8 g (0.494 mol) giving amaximum TAP/K₂-DHTA molar ratio of 1.075.

A 150 ml of pre-mixed phosphate buffer solution (pH=4.7) was dilutedwith 600 ml water and precharged in a coupling vessel and heated to 50°C. while mixing. The basic TAP/K₂-DHTA mixture (pH=10) was added to thecoupling vessel while simultaneously adding 25% aqueous H₃PO₄ to controlthe pH around 4.5. Large amounts of fine light-yellow monomer complexcrystals formed almost immediately and increased during the addition.The final pH was brought to 4.5 while the monomer complex slurry cooledto 30° C. The slurry was filtered giving a pale yellow cake. The monomercomplex cake was washed 3 times with 400 g each of water followed by 200g of ethanol before being set to purge with nitrogen overnight. Thecolor of the cake was pale yellow.

Example D

This example illustrates the effect of production of a monomer complexmade with a 1:1 ratio of TAP and DHTA. The following were combined in aclean dry 2CV Model DIT Mixer (available from Design IntegratedTechnology, Inc, Warrenton, Va.) that was continuously purged withnitrogen gas:

-   -   a) 62.4 grams of polyphosphoric acid (PPA) with a concentration        of 84.84% P₂O₅,    -   b) 14.71 grams of P₂O₅,    -   c) 0.11 grams of tin powder (325 mesh and available from VWR        scientific; this amount is 0.5% based on weight of TD-complex or        0.01421 millimoles Tin/millimoles TD-complex), and    -   d) 22.89 grams of TD-Complex (a one to one complex of        tetraminopyridine (TAP) and dihydroxyterephthalic acid, i.e.,        47.21 g of TAP and 67.21 g of DHTA).

The CV Model was a jacketed twin cone reactor that was heated by thecirculation of hot oil through the jacket. This reactor usedintersecting dual helical-conical blades that intermesh throughout theconical envelope of the bowl. The mixer blades were started and set atabout 53 rpm. The reactor was swept with dry N₂ gas. The temperature ofthe reaction mixture was measured throughout using a thermocouple. Thetemperature of the reaction mixture was raised to 100° C. and held for 1hour. The temperature of the reaction mixture was raised to 137° C. andheld for 3 hours. Next, the temperature of the reaction mixture wasraised to 180° C. and held under vacuum for 3 hours. The mixer waspurged with nitrogen and the polymer solution was discharged into aglass vessel. The polymer was removed from the mixer in the form of asolution in PPA. A sample of the polymer was separated from the solutionand then diluted with methane sulfonic acid (“MSA”) to a concentrationof 0.05% polymer solids. The inherent viscosity of the polymer samplewas 6 dl/g.

Metal Powder Examples. The following examples demonstrate theeffectiveness of tin (Sn), vanadium (V), chromium (Cr) and iron (Fe)metals as reducing agents during polymerization.

Example 5

The following were combined in a clean dry 2CV Model DIT Mixer that wascontinuously purged with nitrogen gas:

-   -   a) 126.5 grams of polyphosphoric acid (PPA) with a concentration        of 85.15% P₂O₅,    -   b) 26.82 grams of P₂O₅,    -   c) 0.23 grams of tin powder (325 mesh and available from VWR        scientific; this amount is 0.5% based on weight of TD-complex or        0.01421 millimoles Tin/millimoles TD-complex), and    -   d) 45.78 grams of TD-Complex (a one to one complex of        Tetraminopyridine (TAP) and dihydroxyterephthalic acid, i.e.        effectively 94.42 g of TAP and 134.42 g of DHTA, an        approximately 10% molar excess of TAP used during preparation).

A CV Model oil heated twin cone reactor having intersecting dualhelical-conical blades that intermesh throughout the conical envelope ofthe bowl was used. The mixer blades were started and set at 53 rpm and avacuum was pulled on the reaction mixture in such a way as to moderatethe foaming of the mixture during the reaction. The temperature of thereaction mixture was measured throughout using a thermocouple. Thetemperature was raised to 100° C. and held for 1 hour. The temperaturewas raised to 137° C. and held for 3 hours. Next the temperature wasraised to 180° C. and held under vacuum for 3 hours. The mixer waspurged with nitrogen and the polymer solution was discharged into aglass vessel. The polymer was removed from the mixer in the form of an asolution in PPA.

A sample of the resulting polymer solution was diluted in methanesulfonic acid (MSA) at a concentration of 0.05% polymer solids. Theinherent viscosity of the polymer sample produced was 23 dl/g. See Table1.

Example 6

The procedure of Example 5 was repeated using 0.01421 millimoles of ironpowder/millimoles TD-complex. The inherent viscosity of the polymersample produced was measured as 29 dl/g. See Table 1.

Example 7

The procedure of Example 5 was repeated using 0.01421 millimoles ofvanadium and chromium powder/millimoles TD-complex. The inherentviscosities of the polymer samples produced were both 22 dl/g usingvanadium and chromium. See Table 1.

Example B

Example 5 was repeated without reducing metal. The resulting inherentviscosity was 9 dl/g. See Table 1

Example C

Example 5 was repeated with the reducing metals copper (Cu), nickel(Ni), manganese (Mn), boron (B), titanium (Ti), aluminum (Al), gallium(Ga), cobalt (Co) and zinc (Zn). The results are shown in Table 2.

Example D

Example 5 was repeated with the metal salts tin chloride and magnesiumchloride used as the reducing agents instead of metal powder. Theresults are shown in Table 3.

TABLE 1 Preferred Metal Reducing Agents % wt mmoles (Based onMetal/mmole Inherent Viscosity Item % Final P₂O₅ % Solids Metal MwMonomer) Polymer (dl/g) Example B 82.5 18 None 9 Example 5 82.5 18 Sn118.7 0.500 0.01421 23 Example 6 82.5 18 Fe 55.8 0.235 0.01421 29Example 7 82.5 18 V 50.94 0.215 0.01421 22 Example 7 82.5 18 Cr 51.9960.219 0.01421 22

TABLE 2 Evaluation of Metal Reducing Agents % wt mmoles (Based onMetal/mmole Inherent Viscosity Polymerization % Final P₂O₅ % SolidsMetal Mw Monomer)* Polymer (dl/g) Example C 82.5 18 Cu 63.5 0.2680.01421 15 Example C 82.5 18 Ni 58.7 0.247 0.01421 16 Example C 82.5 18Mn 54.9 0.231 0.01421 18 Example C 82.5 18 B 10.81 0.046 0.01421 17Example C 82.5 18 Ti 47.88 0.202 0.01421 16 Example C 82.5 18 Zn 65.380.275 0.01421 17 Example C 82.5 18 Al 26.98 0.114 0.01421 17 Example C82.5 18 Ga 69.72 0.294 0.01421 18 Example C 82.5 18 Co 58.93 0.2480.01421 16

TABLE 3 Evaluation of Metal Salt Reducing Agents mmoles % wt Metal(Based on Salt/mmole Inherent Viscosity Polymerization % Final P₂O₅ %Solids Metal Mw Monomer)* Polymer (dl/g) Example D 82.5 18 SnCl₂(H₂O)₂225.63 0.951 0.01421 20 Example D 82.5 18 MgCl₂ 95.23 0.401 0.01421 19

Example 8

Optimization of Reducing Agent During Polymerization. The following werecombined in a clean dry 4CV Model DIT Mixer that was continuously purgedwith nitrogen gas:

-   -   a) 643.94 grams of polyphosphoric acid (PPA) having a        concentration of 84.79% P₂O₅,    -   b) 127.22 grams P₂O₅,    -   c) 2.5 grams of tin powder (325 mesh and available from VWR        scientific; this amount of tin powder is approximately 1.09        weight percent based on the amount of TD Complex), and    -   d) 228.84 grams of TD Complex (a one to one complex of        tetraminopyridine (TAP) and dihydroxyterephthalic acid, i.e.,        effectively 94.42 g of TAP and 134.42 g of DHTA, an        approximately 10% molar excess of TAP used during preparation).

The CV Model was a oil-heated twin cone reactor that used intersectingdual helical-conical blades that intermesh throughout the conicalenvelope of the bowl. The mixer blades were started and set at 53 rpmand a vacuum was pulled on the reaction mixture in such a way as tomoderate the foaming of the mixture during the reaction. The temperatureof the reaction mixture was measured using a thermocouple. Thetemperature was raised to 100° C. and held for 1 hour. The temperaturewas raised to 135° C. and held for 3 hours. Next the temperature wasraised to 180° C. and held for 2 hours. The mixer was purged withnitrogen and the polymer solution was discharged into a glass vessel.The polymer was removed from the mixer in the form of a solution in PPA.

A sample of the resulting polymer solution was diluted in methanesulfonic acid (MSA) at a concentration of 0.05% polymer solids. Theinherent viscosity of this sample was measured as 27 dl/g and wasdesignated Item 1 in Table 4. This procedure was repeated using 0.8,0.5, 0.3, 0.074 and 0% tin based on the weight of TD Complex used. Thetrend of inherent viscosity versus tin content is shown graphically inFIG. 2.

TABLE 4 Inherent Item Polymer Solids % Final P₂O₅ % Tin Powder*Viscosity (dl/g) 1 18 82.1 1.09 27 2 18 82.1 0.8 28.6 3 18 82.1 0.5 29.84 18 82.1 0.3 29.6 5 18 82.1 0.074 17.5 6 18 82.1 0 6.9 *As a percentageof wt TD Complex used.

Fiber Spinning Examples Example 9

Polymerization with Sn (10% molar excess TAP with spun fiber). Thefollowing were combined in a clean dry 4CV Model DIT Mixer that wascontinuously purged with nitrogen gas:

-   -   a) 663.0 grams of polyphosphoric acid (PPA) having a        concentration of 85.15% P₂O₅,    -   b) 112.5 grams P₂O₅,    -   c) 1.1 grams of tin powder (325 mesh and available from VWR        scientific; This amount of Tin powder is approximately 0.5%        weight percent based on the amount of TD Complex), and    -   d) 230.0 grams of TD Complex (a one to one complex of        Tetraminopyridine (TAP) and dihydroxyterephthalic acid, i.e.        94.45 g of TAP and 134.45 g of DHTA).

The 4CV Model was a jacketed twin cone reactor, which was heated by hotoil circulating through the jacket, that used intersecting dualhelical-conical blades that intermesh throughout the conical envelope ofthe bowl. The mixer blades were set at 80 rpm and a vacuum was pulled onthe reaction mixture in such a way as to moderate the foaming of themixture during the reaction. The temperature of the reaction mixture wasmeasured using a thermocouple. The temperature of the reaction mixturewas raised to 100° C. and held for 1 hour. The temperature was raised to135° C. and held for 4 hours. Next the temperature was raised to 180° C.and held for 2 hours. The mixer was purged with nitrogen and the polymersolution was discharged into a glass vessel. The polymer was removedfrom the mixer in the form of a solution in PPA. A sample of the polymersolution was diluted with methane sulfonic acid to 0.05% concentration.The resulting polymer had an inherent viscosity of 26 dl/g.

Fiber Spinning. The polymerized polymer solution in polyphosphoric acid,was spun into a multifilament yarn through a 250 hole spinneret having90 micron diameter holes using a dry-jet-wet spinning technique, withwater being used as the coagulation medium. The air-gap length was 15mm, the spin draw ratio in the air-gap was approximately 14. The bobbinof multifilament yarn was washed in hot (50 C) water for two weeks priorto being dried. The wet yarn was dried at 170 C under a tension of 890 gby passing it through a four-section, 170-inch long tube oven purgedwith nitrogen at a speed of 7 m/min. The resulting 373 denier yarn hadthe following physical properties: tenacity/elongation/modulus 27.8gpd/2.62%/1345 gpd.

Example 10

Polymerization with Fe Metal (10% molar excess TAP with spun fiber). Thefollowing were combined in a clean dry 4CV Model DIT Mixer that wascontinuously purged with nitrogen gas:

-   -   a) 682.1 grams of polyphosphoric acid (PPA) having a        concentration of 85.65% P₂O₅,    -   b) 89 grams P₂O₅,    -   c) 1.15 grams of iron powder (325 mesh and available from        Sigma-Aldrich; This amount of Fe powder is approximately 0.5%        weight percent based on the amount of TD Complex), and    -   d) 228.9 grams of TD Complex (a one to one complex of        Tetraminopyridine (TAP) and dihydroxyterephthalic acid, i.e.        94.45 g of TAP and 134.45 g of DHTA).

The 4CV Model was heated by hot oil and used intersecting dualhelical-conical blades that intermeshed throughout the conical envelopeof the bowl. The mixer blades were started and set at 80 rpm and avacuum was pulled on the reaction mixture in such a way as to moderatethe foaming of the mixture during the reaction. The temperature of thereaction mixture is measured throughout using a thermocouple. Thetemperature of the reaction mixture was raised to 100° C. and held therefor 1 hour. The temperature was raised to 135° C. and held for 4 hours.Next the temperature was raised to 180° C. and held for 2 hours. Themixer was purged with nitrogen and the polymer solution was dischargedinto a glass vessel. The polymer was removed from the mixer in the formof a solution in PPA. A sample of the polymer solution was diluted withmethane sulfonic acid to 0.05% concentration. The n_(inh) was 24 dl/g.

Fiber Spinning. The polymerized polymer solution in polyphosphoric acid,was spun into a multifilament yarn through a 250 hole spinneret having90 micron diameter holes using a dry-jet-wet spinning technique, withwater being used as the coagulation medium. The air-gap length was 20mm, the spin draw ratio in the air-gap was approximately 14. The bobbinof multifilament yarn was washed in boiling water for 90 minutes,followed by soaking in 2 wt % aqueous caustic for 2 hours, followed bysoaking in water for 2 hours, the water being exchanged for fresh watertwice, followed by soaking in 2 wt % aqueous acetic acid for 2 hours,followed by soaking in fresh water for 2 hours, the water beingexchanged for fresh water twice. The bobbin of washed yarn was storedwet in a plastic bag until dried in a tube oven. The yarn was dried at170 C under a tension of 1000 grams by passing it through a 1-foot longtube oven purged with nitrogen at a speed of 0.5 m/min. The resulting387 denier yarn had the following physical properties:tenacity/elongation/modulus 25.9 gpd/2.24%/1398 gpd.

1. A process for making a polyareneazole comprising: contacting a molarexcess in a ratio of at least 1.05 to 1 of a 2,3,5,6-tetraaminopyridinefree base in water with a 2,5-dihydroxy terephthalic acid salt to forman aqueous mixture, adjusting the pH of the aqueous mixture to withinthe range of from about 3 to about 5 to precipitate a monomer complex,and polymerizing the monomer complex to form a polyareneazole having aninherent viscosity of at least about 25 dl/g at 30° C. at a polymerconcentration of 0.05 g/dl in methane sulfonic acid.
 2. The process ofclaim 1 wherein the molar ratio is in excess of about 1.075 to
 1. 3. Theprocess of claim 2 wherein the molar ratio is in excess of about 1.15to
 1. 4. The process of claim 1 wherein the pH is adjusted by addingorthophosphoric acid to the aqueous mixture.
 5. The process of claim 1,wherein the 2,5-dihydroxy terephthalic acid salt is an alkaline salt oran ammonium salt of 2,5-dihydroxy terephthalic acid.
 6. The process ofclaim 5, wherein the alkaline salt is 2,5-dihydroxy terephthalic aciddipotassium salt.
 7. The process of claim 1, wherein the pH of theaqueous mixture is adjusted to within the range of from about 4.3 toabout 4.6 to precipitate the monomer complex.
 8. The process of claim 1,wherein the polyareneazole ispoly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole).9. A process for making a monomer complex comprising: contacting2,3,5,6-tetraminopyridine free base in water with 2,5-dihydroxyterephthalic acid dipotassium salt to form an aqueous mixture, andadjusting the pH of the aqueous mixture to within the range of fromabout 3 to about 5 to precipitate the monomer complex, wherein the molarratio of the 2,3,5,6-tetraminopyridine free base to the 2,5-dihydroxyterephthalic acid dipotassium salt is in excess of about 1.05 to
 1. 10.The process of claim 9 wherein the molar ratio is in excess of about1.075 to
 1. 11. The process of claim 10 wherein the molar ratio is inexcess of about 1.15 to
 1. 12. The process of claim 9 wherein the pH isadjusted by adding dilute orthophosphoric acid to the aqueous mixture.13. The process of claim 9, wherein the pH of the aqueous mixture isadjusted to within a range of from about 4.3 to about 4.6 to precipitatethe monomer complex.